CBS Sports' Jon Heyman reports in a tweet that the negotiations could take a little while to be complete:

https://twitter.com/JonHeymanCBS/status/300720242269749248

Hernandez has pitched 1,620 innings in his eight-year career, all of which has been spent with the Mariners. Hernandez has made the All-Star game three out of the last four seasons and won the AL Cy Young award in 2010.